I. Technical Field
The present invention relates to a solid polymer electrolyte fuel cell, and particularly, to an improvement in the seal structure between an electrolyte membrane electrode assembly and electroconductive separator of a fuel cell.
II. Description of the Related Art
In conventional solid polymer electrolyte fuel cells, a single cell module is used which is constituted by sandwiching a MEA-frame assembly in which a membrane electrode assembly (MEA) is supported by a frame provided with a gasket arranged around its periphery for sealing gas between an anode side electroconductive separator plate and a cathode side electroconductive separator plate. The MEA is constituted of a polymer electrolyte membrane, and an anode bound to one side of this polymer electrolyte membrane and a cathode bound to other side of the polymer electrolyte membrane. Gas supply sections are formed on the periphery of each separator plate to supply fuel gas to the anode and oxidizer gas to the cathode of the MEA, respectively.
However, this conventional solid polymer electrolyte fuel cell, as shown by a sectional view of an electrode-membrane-frame assembly in FIG. 15, gives rise to the occurrence of the so-called cross-leak phenomenon in which a part of the gas supplied to the inside of the battery is discharged through this clearance 303 because a clearance 303 is present between the inside periphery of a frame 300 and an electrode (MEA) 302 with respect to necessity of the assembly of the frame 300 and a separator 301.
Further, for improving this phenomenon, there are a proposal of a structure in which, as shown by a sectional view of an electrode-membrane-frame assembly in FIG. 16, a second gasket 308 is arranged in this clearance 303 and a proposal of a method in which a part of the inside periphery of the gasket is placed to be partially in contact with the outside periphery of the electrode 302 (not shown, see for example, JP-A No. 2005-100970).
Further, the MEA, namely, the polymer electrolyte membrane is incorporated into almost the center of the thickness of the frame and as a binding method thereof, a thermal pressure bonding method, method using an adhesive and a method using a mechanical cramp are adopted.
Further, as a structure of arrangement of the gasket and the like in the electrode-membrane-frame assembly, other various structures are proposed (see, for example, JP-A No. 2006-172752, JP-A No. 2006-310288, JP-A No. 2001-102072, JP-A No. 2005-259465, U.S. Pat. No. 6,610,435 and U.S. Pat. Laid-Open No. 2005/0142414).